1. Field of the Invention
The present invention relates to an expression input apparatus such as a scientific electronic calculator, an expression display apparatus, a method of inputting an expression, a method of displaying an expression, a recording medium storing an expression input control program, and a recording medium storing an expression display control program.
2. Description of Related Art
In conventional expression input apparatuses such as scientific electronic calculators, a plurality of inputted expression portions can be each copied and stored in clipboards to paste intended expression portions (for example, see Japanese Unexamined Patent Application Publication No. 4-252351). In more detail, a technique disclosed in this patent document stores a copied expression portion in association with a number. A user then specifies the number to paste the expression portion associated with the specified number on a cursor position.
In the conventional technique, a user must memorize the relationship between the stored expression portions and the corresponding numbers or operate the apparatus to display the relationship on a display before the pasting. This precludes a smooth pasting operation. Further, the conventional technique is not convenient to replace an expression portion with a character for calculation. In a calculation process, a part of the expression may be replaced with a character for step-by-step calculation. For example, to expand (a+b+c)2, “a+b” is replaced with “A” to expand “(A+c)2”. Then, “a+b” is substituted for “A” in an expanded expression “A2+2Ac+c2” for further expansion. In the conventional technique applied to such a case, when the expression portion “a+b” is copied for use, the “A” replacing “a+b” is not highlighted. Accordingly, a character to be replaced with the expression portion cannot be easily discriminated.